Yeah, no transformer experts here. Nobody here knows what mutual transconductance is, what eddy current and hysteresis losses are, what a B-H curve is about, what impedance matching is, how to calculate turns ratios, or even why iron core transformer cores are made from laminated plates. Best to just forget it.
Go on then, enlighten us all by explaining how mutual transconductance applies to transformers.
The quantity of mu metal used is insignificant, the cost of the material itself is therefore relatively low. I think it is also relatively easy to form so that isn't a problem either. Empire phonograph cartridge bodies were usually made from them to shield them from magnetically induced hum, even the cheap ones. It is ideally suited for this purpose. Wood used by some manufacturers is entirely useless in this regard. Mu metal is usually used for shielding magnetic fields especially from induced hum, not in transformer cores. Transformer cores are usually made from permalloy and supermalloy because they are magnetically very soft and have high flux saturation points in the vacinity of 15,000 gauss (tall skinny B-H curves that are nearly vertical.) Magnetic coercivity is very low. These core material metals are usually aluminium killed nickel alloy steels while mu metal is a molybdenum copper nickel iron alloy.
Mu-metal - Wikipedia, the free encyclopedia
Permalloy - Wikipedia, the free encyclopedia
Supermalloy - Wikipedia, the free encyclopedia
I can't. Nobody here incuding me knows anything about it. Didn't you understand what JC said? We here are all clueless in this area.
I'll try to avoid colorful writing in the future lest I continue to confuse you.
Really, getting 20dB of gain, 100+dB of CMR, galvanic isolation, and all that with no significant noise penalty- they're pretty inexpensive for what they do. No need to justify the price- the performance speaks for itself.
If I were in the position of designing a top-quality preamp for commercial production, I'd be foolish not to closely examine all of the top candidates, much less dismiss the idea of input transformers out of hand. For my one-off, I used the Sowters as "known-good" and in that specific instance, available to me very cheaply since Morgan had a couple of extras left over and was worried that they might "accidentally" find their way into my suitcase.
You're the only one I'm aware of claiming that it actually is an area pertaining to transformers. So go on, tell us how you know this. Enquiring minds...
Perhaps I should remind us that the fundamental difference between amateurs and professionals is not competence, but how much money they take off other people. In some cases professionals like to arrange themselves into exclusive clubs, and will not permit other people to sell their services without being admitted to the club. It seems that this is only wrong when factory workers do it.
Amateurs do something because they love doing it. They may, or may not, be as competent as a professional, or more competent. They may, or may not, be as well qualified in the formal sense as a professional, or better qualified.
I think I should also say that most professionals remember their manners. When challenged by an amateur they deal with the issue, rather than the person. They keep their crowing for their adverts, not technical discussions.
Amateurs do something because they love doing it. They may, or may not, be as competent as a professional, or more competent. They may, or may not, be as well qualified in the formal sense as a professional, or better qualified.
I think I should also say that most professionals remember their manners. When challenged by an amateur they deal with the issue, rather than the person. They keep their crowing for their adverts, not technical discussions.
I refer the right honourable gentleman to the reply I gave some moments ago
(#10826)
All of which can be achieved by a lump of iron at a knock-down price. Seems the continued confusion isn't mine after all
Yes, I should have also added "...and vanishingly low distortion."
Joachim, forgive me for using you as an example to this 'confusion' comparing transformers. In a recent input you mention someone else comparing a Sowter with a Jensen transformer. As far as THAT goes, this is OK, however YOU use a Lundahl transformer, yourself. Where does IT fit into this comparison? Are you saying to us that you bought the WRONG transformer? Are you saying to us that it doesn't matter WHAT brand transformer we buy, as they are all virtually perfect (a view held by many here). What are we to determine from all this?
The ONLY person who gave any REAL input was Soundminded, when he mentioned transformer laminations and the core material differences. The rest of you are apparently ... on the subject of what an audio input transformer is composed of, its actual behavior under low level conditions, and its excess noise contributions. I learned about these problems when working in the Ampex Audio Department, and THAT is why I have tried for the last 40+ years to eliminate them from the audio path, if and when possible. Please forgive me, if I have yet again overstepped the boundary of social respectability by bringing this out.
The ONLY person who gave any REAL input was Soundminded, when he mentioned transformer laminations and the core material differences. The rest of you are apparently ... on the subject of what an audio input transformer is composed of, its actual behavior under low level conditions, and its excess noise contributions. I learned about these problems when working in the Ampex Audio Department, and THAT is why I have tried for the last 40+ years to eliminate them from the audio path, if and when possible. Please forgive me, if I have yet again overstepped the boundary of social respectability by bringing this out.
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Please, I'm all ears. I have not observered this in even the cheapest Calrad mike transformers.
Number 2 is due Friday, boy this time he'll get my 1953 Lionel set. I meant excess noise in a transformer easily measured, as usual BTW not a single reference in the technical literature.
I assume the winding resistance acts like a wirewound resistor, one of the best as you have stated numerous times. Maybe I'm barking up the wrong tree?
I just Googled 'audio transformer eddy current' and got lots of replies. You might compare Sowter's notes on the matter, for example, but I used to measure transformer noise with frequency as predicted by Q meter vs frequency readings of input transformers. I would just love to get a Calrad transformer tested. Beyer was bad enough!
Congrats!
The more common term used for transformers is "noise figure," which is expressed in dB (i.e. the difference between an ideal and realworld transformer).
Right. The "excess noise" is largely the thermal noise produced by the transformer's winding resistances.
Another source of noise is Barkhausen noise.
se
I thought this might be of interest and I would like to find out if its still possible to be off topic in this thread
Super sense of smell not innate
rgds
james
Super sense of smell not innate
rgds
james
I thought this might be of interest and I would like to find out if its still possible to be off topic in this thread
Super sense of smell not innate
rgds
james
This is indeed a well known phenomenon. If you start to do something that is new to you, be it playing the violin or running a steeple chase, you have to do it over and over again so that the brain can develop the motor patterns needed. The more you do it, the quicker the brain can call up the required patterns and the more automatic this becomes. More 'brain power' can than be diverted from the process to tackle other tasks.
This is a typical process found in most living creatures and is called 'learning'
jan didden
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